1. Field of the Invention
The invention relates to a rotary connector for electrically connecting an electric device disposed on the rotor side of a steering device and an electric device disposed on the stator side and particularly to the structure of a locking mechanism for preventing relative rotation of a housing prior to installation on a steering device.
2. Description of the Prior Art
A rotary connector has been mainly provided with a pair of housings disposed concentrically and connected to be relatively rotatable, and a flexible cable stored in a cable storing part formed between the paired housings to be wound and unwound, both ends thereof being led through to the outside. One housing is fixed to a steering column of a steering device, the other housing is fixed to a steering wheel, and both ends of the flexible cable are connected to an electric part provided on the steering column side and an electric part provided on the steering wheel side, respectively to be used as electric connecting means of an air bag system, a horn circuit and the like.
The winding amount and unwinding amount of the flexible cable, that is, the moving amounts of the movable housing from the neutral position in one direction and in the other direction to the stationary housing are both limited, and respectively set a little larger than the counterclockwise moving amount and the clockwise moving amount from the neutral position of the steering wheel. Accordingly, in installing the rotary connector on the steering device, it is necessary to strictly align the neutral position of the steering wheel with the neutral position of the rotary connector to prevent the occurrence of the disadvantage that the flexible cable is wound up in one direction or in the other direction by the steering wheel operation so that excessive tension is applied to the flexible cable to cause breakage. Accordingly, a rotary connector has been previously proposed, having a locking mechanism for locking a stationary housing and a movable housing set in a neutral position to the stationary housing to prevent rotation between both housings prior to installation onto a steering device, and automatically releasing locking between both housings with installation of the rotary connector onto the steering device to enable the movable housing to rotate with the steering wheel operation.
FIG. 10 is a sectional view of this type of a rotary connector which has been known heretofore, and FIG. 11 is a bottom view of the principal part showing the engagement state of a locking key provided on the rotary connector of FIG. 10 with a stationary housing. In the drawings, the reference numeral 100 designates a movable housing, 200 a stationary housing, 300 a flexible cable, 400 a rotor snap, 500 a locking key structure, and 600 a spring member for urging the locking key mechanism 500 in one direction.
The movable housing 100 is constituted of a disc-like top plate 103 provided with a center hole 101 and a first conductor lead-through part 102 formed for fixing one end of the flexible cable 300, and a first inner cylinder 104 suspended from the inner peripheral edge of the top plate 103. A snap claw 105 for snap-joining the rotor snap 400 is formed on the inner surface of the first inner cylinder 104. The first inner cylinder 104 is provided with a guide hole 106 bored in a part thereof to penetrate from the tip thereof to the surface of the top plate 103.
On the other hand, the stationary housing 200 is constituted of a disc-like base plate 203 provided with a center hole 201 having such a diameter as to pass the first inner cylinder 104 therethrough, and a second conductor lead-through part 202 formed for fixing the other end of the flexible cable 300, and an outer cylinder 204 raised from the outer peripheral part of the base plate 203. The base plate 203 and the outer cylinder 204 are joined and united in a body by heat caulking or the like. The inner peripheral edge of the base plate 203, as shown in FIG. 11, has a key engaging part 205 recessed for engaging with the tip of the locking key 501 constituting the other part of the locking key structure 500.
The flexible cable 300 is spirally wound and stored in an annular cable storing part 111 formed by the concentric combination of the moving housing 100 with the stationary housing 200. One end of the flexible cable 300 is wired and fixed in the first conductor lead-through part 102 to be connected to a lead wire or an external connector not shown in the first conductor lead-through part 102, and electrically led through to the outside of the moving housing 100. The other end of the flexible cable 300 is wired and fixed in the second conductor lead-through part 202 to be connected to a lead wire or an external connector not shown in the second conductor lead-through part 202, and electrically led through to the outside of the stationary housing 200. The constitution of the flexible cable and the connecting structure of the flexible cable and the lead wire or the external connector are known and not the gist of the present invention, so the description is omitted.
The rotor snap 400 is intended to rotatably connect the movable housing 100 to the stationary housing 200, and constituted of a doughnut-like locking plate 402 provided with a center hole 401 having a diameter smaller than the inside diameter of the first inner cylinder 104 and having an outside diameter smaller than the outside diameter of the base plate 203, and a second inner cylinder 403 raised from the inner peripheral part of the locking plate 402. A portion of the locking plate 402 opposite to the guide hole 106 is provided with an escape hole 404 for preventing the locking key 501 from colliding with the locking plate 402, and the second inner cylinder 403 has an engagement hole 405 for engaging with the snap claw 105 formed on the first inner cylinder 104.
The locking key structure 500 is formed by the metal locking key 501, the tip of which is bent L-shaped, and a resin-made operating part 502 secured to the tail end of the locking key 501. A pair of snap joining units (not shown) are formed on the connecting part of the respective members 501, 502. After the operating part 502 and the spring member 600 are stored in the guide hole 106 bored in the movable housing 100, the tail end of the locking key 501 is inserted in the guide hole 106 from below the guide hole 106, and the snap joining means (not shown) formed on the tail end of the locking key 501 and the snap joining means (not shown) formed on the tail end of the operating part 502 are connected to thereby integrally connect the locking key 501 and the operating part 502 to each other.
At the time of shipping, the position in the rotating direction of the movable housing 100 is adjusted to the neutral position to the stationary housing 200, and the locking key 501 is engaged with the key engaging part 205 formed on the base plate 203 of the stationary housing 200. The tip of the operating part 502 is projected outward from the top plate 103 by the elastic force of the spring member 600.
The thus constructed rotary connector is, as shown in FIG. 10, installed on a steering device by passing a steering shaft 700 through a central through hole of the rotary connector, aligning the steering shaft 700 with the neutral position of the stationary housing 200, then fixing the stationary housing 200 to the steering column 701, fitting a steering wheel 702 to the steering shaft 700, and connecting the steering wheel 702 and the movable housing 100 to each other. The steering wheel 702 is mounted on the steering shaft 700 by passing the steering shaft 700 through a through hole 704 bored in the central part of a steering wheel hub 703 and bringing one side of the steering wheel hub 703 into contact with an engaging stepped part 705 formed on the steering shaft 700, and in that case, the steering wheel hub 703 abuts on the operating part 502 of the locking key structure 500 prior to abutting on the engaging stepped part 705 to force the operating part 502 into the guide hole 106 against the elastic force of the spring member 600.
The locking key structure 500 has the locking key 501 and the operating part 502 integrated with each other, so that the locking key 501 is also moved for the forced amount of the operating part 502. In the moving process, the engagement of the locking key 501 with the key engaging part 205 formed on the stationary housing 200 is released so that the movable housing 100 can be rotated to the stationary housing 200. In the stage where one side of the steering wheel hub 703 abuts on the engaging stepped part 705 formed on the steering shaft 700, as indicated by a one-dot chain line in FIG. 10, the tip of the locking key 501 is passed through the escape hole 404 bored in the locking plate 402 of the rotor snap 400 and projected to the outside of the rotor snap 400.
As described above, the conventional rotary connector with the locking mechanism has the problem that when the steering wheel 702 is mounted on the steering shaft 700, the steering wheel hub 703 presses the operating part 502 so that the tip of the locking key 501 is projected to the outside of the rotor snap 400, resulting in the disadvantage that other vehicle-mounted parts cannot be disposed in a portion contacting the rotor snap 400, so the portion becomes dead space to cause the difficulty of designing the periphery of the steering device in an automobile.
Since the rotary connector has the locking key 501 and the operating part 502 integrated with each other so that the locking key 501 is also moved for the forced amount of the operating 502, the projection amount of the locking key 501 from the rotor snap 400 varies depending on the setting errors of the rotary connector and the steering wheel handle 702 to the steering shaft 700. On the other hand, the dimensions of the dead space preset between the rotary connector and the other on-vehicle part vary depending on the setting errors of the rotary connector and other vehicle-mounted parts to the steering shaft 700. Accordingly, in the case of some setting errors of the rotary connector and the steering wheel 702 to the steering shaft 700 and some setting errors of the rotary connector and other vehicle-mounted parts, the locking key 501 abuts on other vehicle-mounted parts set through the dead space, resulting in the risk of causing the disadvantage such as generation of abnormal sound.
The present invention has been made in order to overcome the above disadvantages of the prior art and provides a rotary connector which may eliminate the dead space between the rotary connector and other vehicle-mounted parts by preventing projection of a locking key from a housing, and will not cause generation of abnormal sound to be excellent in reliability.
According to a first aspect of the present invention, a rotary connector includes movable and stationary housings disposed concentrically and connected to be relatively rotatable, a flexible cable stored to be wound and unwound in an annular cable storing part formed between two housings, and a locking mechanism provided between the movable and stationary housings, the locking mechanism has a guide hole bored in the movable housing, an operating part slidably stored in the guide hole, a part of which is projected from one open end of the guide hole to the outside, a locking key slidably stored in the guide hole, a part of which is projected from the other open end of the guide hole to the outside, a stopper disposed opposite to the locking key, a first spring member set between the operating part and the locking key, a second spring member set between the locking key and the stopper, and a key engaging part with which the locking key provided on the stationary housing is removably engaged, and when the operating part is forced into the guide hole, the locking key is subjected to external force corresponding to a difference between the elastic force of the first spring member and the elastic force of the second spring member and moved to the stopper side, thereby releasing the engagement of the locking key with the key engaging part, and after the locking key is forced to abut on the stopper, only the first spring member is elastically deformed to force the operating part into the guide hole.
The operating part and the locking key are thus constituted as independent separate bodies, the first spring member is set between the operating part and the locking key, and the second spring member is set between the locking key and the stopper, whereby when the operating part is forced into the hole by a steering wheel hub, external force corresponding to a difference between the elastic force of the first spring member and the elastic force of the second spring member is applied to the locking key so that the locking key is pushed down in the pressing direction of the operating part to release the engagement of the locking key with the key engaging part, thereby enabling relative rotation between the movable housing and the stationary housing. When the operating part is further pressed under such a condition, the locking key abuts on the stopper to prevent the locking key from projecting to the outside. Accordingly, it is not necessary to provide dead space between the rotary connector and other vehicle-mounted parts, and further the locking key is kept from abutting on other vehicle-mounted parts to generate abnormal sound so as to facilitate designing the periphery of a steering device. Further, after the locking key abuts on the stopper, the operating part is separately forced into the guide hole against the elastic force of the first spring member, so that setting errors of the rotary connector and the steering wheel to the steering shaft can be absorbed by the elastic deformation of the first spring member not to cause any special problem.
According to another aspect of the invention, the movable housing to be used includes a disc-like top plate having a center hole, and an inner cylinder suspended from the inner peripheral edge of the top plate, the stationary housing to be used includes a base plate having a center hole penetrating the inner cylinder and an outer cylinder raised from the outer peripheral edge of the base plate, the inner cylinder is provided with the guide hole penetrating from the tip thereof to the surface of the top plate, and the key engaging part is formed on the base plate.
In the rotary connector having the thus constructed housing, the inner cylinder is provided with the guide hole bored to penetrate from the tip thereof to the surface of the top plate, whereby large installation space for the locking mechanism can be taken, and the locking mechanism including the operating part, the locking key and the first and second spring members can be easily set.
According to another aspect of the invention, as the stopper, used is a rotor snap rotatably connecting the movable and stationary housings to each other.
When the rotor snap is thus used as the stopper for bearing the second spring member, the number of the parts can be decreased so that the constitution of the rotary connector can be simplified and the manufacturing cost can be reduced.